1. Field of the Invention
This invention relates to a method and apparatus for repairing partially filled vias, defective vias, and filling empty vias within a ceramic product greensheet and, more particularly, to using a tool comprising a punch head assembly, a product greensheet assembly and a transfer greensheet assembly in which a punch head assembly locates the via to be repaired or filled, is used to move and position a transfer greensheet containing filled vias over the product greensheet and a via of the transfer greensheet is punched by the punch head of the punch head assembly to repair and/or fill the via.
2. Description of Related Art
Ceramics have found widespread use in the electronics industry as a substrate for integrated circuit packages. In general, metalized circuit patterns are applied to a ceramic substrate which is in the form of an unsintered greensheet, and a plurality of the metalized ceramic greensheets are stacked and laminated and co-sintered to create a monolith of substrate and three-dimensional metal circuitry. The ceramic greensheets are constructed by combining ceramic particles and organic binders and forming into unfired, or “greensheet,” tape.
The casting of suspensions of ceramic material to form layers or greensheets which are then laminated and sintered to make a ceramic substrate electronic article is well known in the art. The doctor blade method is one method for making a ceramic greensheet and typically, ceramic powder is mixed with an organic solvent, a plasticizer and a binder forming a slurry, the slurry is cast in a regulated thickness on a carrier film with the aid of a doctor blade, and the applied layer of the slurry and carrier film is then dried. The ceramic containing formula typically uses a ceramic such as alumina and a butyral type resin like polyvinyl butyral as the binder.
Once the greensheets are formed, via holes are formed in a predefined pattern in the greensheet and the via holes then filled with a conductive paste. Metal lines in a form of circuitry connecting the vias are then formed on the surface of the greensheet by screening or extrusion printing with the conductive paste. The conductive paste is formed of a suitable particulate metallic material such as molybdenum or copper, which will withstand the subsequent sintering process. The metalized sheets are then stacked, laminated, and fired in an appropriate atmosphere to form a monolithic MLC substrate with complex internal circuitry.
Due to the ever increasing complexity of microelectronic packaging, greensheet patterns are becoming ever more difficult to fabricate defect free. With patterns containing several hundred thousand vias per greensheet, even a single unfilled or partially filled via renders the entire greensheet useless.
Bearing in mind the problems and deficiencies of the prior art, it is therefore an object of the present invention to provide a method for filling vias in a ceramic greensheet.
It is another object of the present invention to provide a method for repairing vias in a ceramic greensheet.
A further object of the invention is to provide an apparatus for filling vias in a ceramic green sheet.
It is yet another object of the present invention to provide an apparatus for repairing vias in a ceramic greensheet.
Another object of the invention is to provide a viewing system for use with the apparatus and method.
Still other objects and advantages of the invention will in part be obvious and will in part be apparent from the specification.